WCF and HTTP Error 404.3 – Not Found
In the web world, a 404 error is usually self-explanatory–whatever page you’re requesting simply isn’t there.
However, there are different variations of the 404 error. The 404.3 error is different from the typical 404 error in that the item you request may actually exist on the server. It’s just that the server can’t process it. One of the descriptions that you might get with this is
The page you are requesting cannot be served because of the extension of the configuration. If the page is a script, add a handler. If the file should be downloaded, add a MIME map.
If you’re attempting to access a WCF service, the issue may be that the web server may not have WCF correctly installed and configured. To solve this problem, execute the Service Model Registration tool to enable WCF on IIS. To do so, just run the following from a command line as an Administrator:
"%windir%\Microsoft.NET\Framework\v3.0\Windows Communication Foundation\ServiceModelReg.exe" -r -y
The following article provides a great step-by-step on how to setup a WCF service on IIS 7, including the above step to register WCF components: